On the Tip of the Tongue: Explanations for Burning Mouth Syndrome
A burning feeling on the tongue or roof of the mouth can usually be traced to a steaming cappuccino, or maybe to hot mozzarella dripping from a slice of fresh pizza. But in some people, particularly postmenopausal women, a debilitating burning sensation in the mouth can develop out of the blue. And then it never leaves.
Burning mouth syndrome was once considered one of the many symptoms "nervous" older women invented for themselves. But new research now suggests that it is linked to taste changes in mouth. Below, Miriam Grushka, DDS, PhD, an associate professor of oral medicine at University of Illinois in Chicago, discusses common causes and treatments for burning mouth syndrome.
What is burning mouth syndrome?
It's defined as a constant burning sensation in the mouth that's usually present in the tongue and often on the palate, but it can be anywhere. It often starts suddenly and then it can continue for months or years. People complain that their mouth feels as though they had been burnt with hot coffee, except it just doesn't go away.
The burning sensation usually gets worse over the day. So it's not too bad in the morning, then it gets worse after the first meal of the day and then it peaks in the late afternoon or by early evening. Once people go to sleep, the pain usually disappears. And then when they wake up in the morning, they feel fine. And the cycle keeps repeating itself.
Are there any other symptoms associated with burning mouth syndrome?
Very commonly, it's associated with a metallic or bitter taste in the mouth that also gets worse over the day. A lot of people complain about dry mouth. But when you look in the mouth and check the flow of saliva it's normal.
These symptoms are often very severe. There have been a lot of studies looking at the psychological impact and if burning mouth syndrome is severe and ongoing, it can cause a lot of depression and anxiety. The pattern of changes is very similar to what's seen in other people who have chronic pain.
How is burning mouth syndrome usually diagnosed?
Until recently, the diagnosis was typically based on the clinical symptoms. It has been a diagnosis of exclusion, so that people were tested to see if they had an oral yeast infection or a vitamin deficiency or diabetes. And if they had none of those changes and their mouth looked normal and they had the typical pattern of burning, they ended up with a diagnosis of burning mouth.
More recent research shows the association between burning mouth and taste changes. Dr. Linda Bartoshuk at Yale has found is that there is almost a footprint of the disorder—a loss of bitter taste at the tip of the tongue. We can check the ability to taste sweet, sour, salt and bitter flavors at the front and then at the back of the tongue using a spatial taste-test. So someone with burning mouth syndrome may have normal tastes or somewhat reduced tastes for sour, sweet and salty flavors but the ability to taste bitter flavors, which is located at the tip of the tongue, is often gone.
The theory is that taste inhibits pain and, if there's a problem with taste (like loss of bitter taste at the tip of the tongue), there's a loss of inhibition of the pain fibers, so someone spontaneously begins to produce pain. And the pain is interpreted as burning mouth pain.
Another test is performed using a local anesthetic. When a local anesthetic is applied to the tip of their tongue where they have the burning, the pain often gets worse instead of getting better.
Who gets burning mouth syndrome?
It's most common in women after menopause. One of the reasons that this problem is found in older women relates to the loss of estrogen that occurs in the menopausal period and that causes a loss of bitter taste buds. We do see men with burning mouth, but it's less common. Sometimes I see younger people with it, but it is usually associated with a benign condition called geographic tongue. Geographic tongue causes inflammation on the surface of the tongue causing red patches that come and go and move around. That might affect the taste buds which then leads to the loss of pain inhibition and burning mouth.
What can increase the risk?
When the bitter taste is lost within the taste bud, the pain fibers surrounding that bud are the ones that experience a loss of inhibition and start becoming painful. An infection, a nutritional deficiency of B12, folate or iron can also damage taste buds.
And just to make it a little bit more complex, the people who are most at risk of developing burning mouth are called super-tasters—people who have the greatest number of taste buds on the tip of the tongue. This is a genetic difference: some people are non-tasters, some are medium-tasters and some are super-tasters. Flavors are much more intense for super-tasters, and they have different taste preferences than non-tasters and medium-tasters. Women are much more likely to be super-tasters than men. So most people with burning mouth syndrome are super-tasters who have had a taste loss for some reason.
People who do a lot of clenching are at increased risk. They keep their tongue pressed tightly against their teeth at night and they end up with their tongue scalloped. When the clenching is controlled, through medication or the use of mouth guards, they often feel better.
Are underlying medical conditions associated with burning mouth syndrome?
Certain conditions such as Sjögren's syndrome, diabetes, thyroid disease and liver dysfunction have been associated with burning mouth syndrome, but it just doesn't occur very often in these people. For example, most people with Sjögren's syndrome have very dry mouth and almost all of them have a yeast infection as a result. When the majority of Sjögren's patients are treated with antifungal medication, they no longer have burning mouth.
Can anxiety and depression cause burning mouth syndrome?
There have been many studies looking at the psychological profiles of burning mouth people, and almost all of them have found that there are psychological changes in this group of people. Twenty years ago, it was thought that anxiety and depression were what caused the changes. But with the more recent literature, it's assumed that the change in psychological profile is the result of the chronic pain rather than the cause of the chronic pain.
The thrust of the research now is looking at the organic changes rather than looking at a psychological profile and saying that these people are depressed and anxious.
Do any medications cause burning mouth syndrome?
ACE (angiotensin-converting enzyme) inhibitors, which are taken for high blood pressure, can cause burning mouth. Even when people go off the ACE inhibitors, the pain doesn't usually go away without treatment.
What can ease symptoms of burning mouth syndrome?
People often will chew ice chips. And I'm not sure if it's the cold or the fact that there's something in the mouth that helps to reduce the pain. Most typically people say they chew gum all day because that's seems to be the greatest help.
Are there any medications for burning mouth syndrome?
There is nothing specifically approved for burning mouth syndrome but some drugs approved for other conditions have been helpful. The drug of choice right now is Klonopin (clonazepam), which is a benzodiazepine. We think it works in the taste system and it inhibits spontaneous pain. Once people respond to medication, they often get better quickly and can start decreasing their medications. We often combine the clonazepam with Neurontin (gabapentin). And we sometimes use a third medication, Lamictal (lamotrigine), which is an anticonvulsant used to treat epilepsy.
Tricyclic antidepressants were used a lot in the '80s, because that's all there was. I think they're used much less now because there are a lot of side effects for a very small benefit.
Can people ever recover without medication?
Yes, we have early data from when we had much poorer medication to control it and we found two-thirds of people have spontaneous remission even with no medication. People usually had pain for three to five years before it remitted spontaneously. We think it's because of regeneration of the taste buds.